1. Field of the Invention
This invention relates to providing a semitrailer antitheft system. More particularly, this invention concerns a semitrailer antitheft system for mechanically locking the gear train of a semitrailer landing gear system, thereby preventing unauthorized movement of the semitrailer.
2. Description of the Prior Art
Typically, semitrailers (herein referred to as trailers) are used to transport goods over the open roads by attaching the trailer to semi truck (herein referred to as tractor). Upon delivering the goods to the desired destination, the trailers are either uncoupled from or remained coupled to the tractor. To facilitate the coupling and uncoupling of the tractor from the trailer, many trailers come equipped with jack-type devices which are known by such names as "landing gear" or "props" which are mounted on each side of and adjacent to the front end of the trailer. A typical landing gear system comprises a substantially enclosed gear train consisting of, in some cases, a drive gear mounted on a slidable shaft and a driven gear mounted on a stationary shaft. The stationary shaft is coupled, typically by a bevel gear, to a telescoping lower strut which, in turn, is slidably attached to a stationary upper strut member.
In operation, extension of the lower strut is accomplished by turning a lever arm or handle which is attached to the slidable shaft. The output torque from the slidable shaft-mounted drive gear is transferred to the stationary shaft-mounted driven gear which, in turn, causes rotation of the stationary shaft and a resulting vertical movement of the lower strut. Successive rotations of the handle causes a "foot", attached to the bottom of each lower strut, to come in contact with the ground. Any further rotations of the handle results in a raising of the upper end of the trailer. With the trailer being supported adjacent the front end of the trailer by the landing gear, the trailer's kingpin may then be disengaged from the tractor's swivel plate thereby allowing for the removal of the tractor. Upon re-coupling of the same or different tractor to the trailer, if the landing gear is not raised to a sufficient height above the ground level after coupling to the tractor, any attempts to move the trailer without raising the landing gear will result in the landing gear feet dragging noisily along the ground surface and striking any elevated protuberances in the road, thereby causing damage to the landing gear, the trailer, or both.
Due to the fact that trailers oftentimes contain large amounts of valuable cargo, unless the cargo contained in the trailer is immediately attended to, or the trailer is stored in a safe location, the trailer and its cargo make an appealing target to a would-be thief and are thus vulnerable to theft. Typical methods of stealing a trailer and its cargo include coupling a tractor to the uncoupled trailer, raising the landing gear, and towing the trailer away. If the tractor is coupled and left unattended, a thief may either steal the tractor-trailer combination or uncouple the original tractor from the trailer and replace it with the thieves tractor.
Applicant is aware of prior art attempts to incorporate locking devices into semitrailer landing gear units. For example, Rimbaud et al. U.S. Pat. No. 5,426,961 teaches the use of a keyed locking device attached to the interior of the gear train housing which incorporates a forked lever to catch and immobilize the drive gear/moveable shaft. Though this device may be adequate for its intended purpose, it is susceptible to being circumvented by using a large lever arm such as a pipe wrench to manually turn the transfer shaft connecting the two landing gear units.
Still another landing gear locking mechanisms is disclosed in Blakelock GB-A-1,565,542 which teaches a mechanical keyed lock mechanism attached to the interior upper portion of the upper strut member. Locking of the landing gear is accomplished by a key-activated retractable bar which is structured and arranged to engage a space between the gear teeth on a bevel gear mounted within the upper strut housing, thereby preventing movement of the lower strut member. Though this arrangement may also be adequate for its intended purpose, it is easily accessible and hence susceptible to tampering after removal of the upper strut housing cover plate.
Thus, there exists an unmet need for a method to safeguard a semitrailer and its contents that is both relatively impervious to circumvention and unauthorized tampering and simple and economical to use.